1. Field of the Invention
The present invention relates to coated cemented carbide inserts (cutting tools), particularly useful for wet or dry milling of steels at high cutting speeds, milling of hardened steels, and high feed copy milling of tool steels.
2. Description of the Related Art
When machining low and medium alloyed steels and hardened steels with cemented carbide tools, the cutting edge is worn according to different wear mechanisms, such as chemical wear, abrasive wear, adhesive wear and by edge chipping caused by cracks formed along the cutting edge. The domination of any of the wear mechanisms is determined by the application, and is dependent on properties of the machined material, applied cutting parameters, and the properties of the tool material. In general, it is very difficult to improve all tool properties simultaneously, and commercial cemented carbide grades have usually been optimized with respect to one or few of the above mentioned wear types, and have consequently been optimized for specific application areas.
EP 1493845 relates to a coated cemented carbide insert (cutting tool), particularly useful for milling of stainless steels and super alloys but also milling of steels in toughness demanding applications. The cutting tool insert is characterised by a cemented carbide body comprising WC, NbC and TaC, a W-alloyed Co binder phase, and a coating comprising an innermost layer of TiCxNyOz with equiaxed grains, a layer of TiCxNyOz with columnar grains and a layer of α-Al2O3.
WO 2007/069973 discloses a coated cutting tool insert particularly useful for dry and wet machining, preferably milling, in low and medium alloyed steels, stainless steels, with or without raw surface zones. The insert is characterized by a WC—TaC—NbC—Co cemented carbide with a W alloyed Co-binder phase and a coating including an innermost layer of TiCxNyOz with columnar grains and a top layer at least on the rake face of a smooth α-Al2O3.
WO 01/16389 discloses a coated milling insert particularly useful for milling in low and medium alloyed steels with or without abrasive surface zones during dry or wet conditions at high cutting speed, and milling of hardened steels at high cutting speed. The insert is characterized by WC—Co cemented carbide with a low content of cubic carbides and a highly W-alloyed binder phase and a coating including an innermost layer of TiCxNyOz with columnar grains and a top layer of TiN and an inner layer of κ-Al2O3.
EP 1352697 provides coated cemented carbide inserts (cutting tool), particularly useful for milling at high cutting speed in steels and milling in hardened steels. The inserts are characterized by a WC—Co cemented carbide containing NbC and TaC and a W-alloyed binder phase and a coating including a first, innermost layer of TiCxNyOz with equiaxed grains, a layer of TiCxNyOz with columnar grains and at least one layer of Al2O3 consisting essentially of the κ-phase.
What is needed is a coated cutting tool with enhanced performance for milling of steels, hardened steels, and tool steels. The invention is directed to these, as well as other, important needs.